Ticket #23850: 23850.4.diff

wp-includes/theme.php

@@ -1264 +1264 @@
                                 $args[0] = array_intersect( $args[0], array_keys( get_post_format_slugs() ) );
                         break;
 
+                case 'html5' :
+                        // 'html5' must take a second argument of what should be html5
+                        if ( 1 === func_num_args() ) {
+                                trigger_error( "add_theme_support( 'html5', \$what ) requires a second argument.", E_USER_WARNING );
+                                return false;
+                        }
+
+                        // Calling 'html5' again merges, rather than replaces.
+                        if ( isset( $_wp_theme_features['html5'][0] ) )
+                                $args[0] = array_merge( $_wp_theme_features['html5']['0'], $args[0] );
+
+                        break;
                 case 'custom-header-uploads' :
                         return add_theme_support( 'custom-header', array( 'uploads' => true ) );
                         break;